libsanitizer/sanitizer_common/sanitizer_unwind_linux_libcdep.cc

   1 //===-- sanitizer_unwind_linux_libcdep.cc ---------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file contains the unwind.h-based (aka "slow") stack unwinding routines
   9 // available to the tools on Linux, Android, NetBSD, FreeBSD, and Solaris.
  10 //===----------------------------------------------------------------------===//
  11
  12 #include "sanitizer_platform.h"
  13 #if SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD || \
  14     SANITIZER_SOLARIS
  15 #include "sanitizer_common.h"
  16 #include "sanitizer_stacktrace.h"
  17
  18 #if SANITIZER_ANDROID
  19 #include <dlfcn.h>  // for dlopen()
  20 #endif
  21
  22 #if SANITIZER_FREEBSD
  23 #define _GNU_SOURCE  // to declare _Unwind_Backtrace() from <unwind.h>
  24 #endif
  25 #include <unwind.h>
  26
  27 namespace __sanitizer {
  28
  29 //------------------------- SlowUnwindStack -----------------------------------
  30
  31 typedef struct {
  32   uptr absolute_pc;
  33   uptr stack_top;
  34   uptr stack_size;
  35 } backtrace_frame_t;
  36
  37 extern "C" {
  38 typedef void *(*acquire_my_map_info_list_func)();
  39 typedef void (*release_my_map_info_list_func)(void *map);
  40 typedef sptr (*unwind_backtrace_signal_arch_func)(
  41     void *siginfo, void *sigcontext, void *map_info_list,
  42     backtrace_frame_t *backtrace, uptr ignore_depth, uptr max_depth);
  43 acquire_my_map_info_list_func acquire_my_map_info_list;
  44 release_my_map_info_list_func release_my_map_info_list;
  45 unwind_backtrace_signal_arch_func unwind_backtrace_signal_arch;
  46 } // extern "C"
  47
  48 #if SANITIZER_ANDROID
  49 void SanitizerInitializeUnwinder() {
  50   if (AndroidGetApiLevel() >= ANDROID_LOLLIPOP_MR1) return;
  51
  52   // Pre-lollipop Android can not unwind through signal handler frames with
  53   // libgcc unwinder, but it has a libcorkscrew.so library with the necessary
  54   // workarounds.
  55   void *p = dlopen("libcorkscrew.so", RTLD_LAZY);
  56   if (!p) {
  57     VReport(1,
  58             "Failed to open libcorkscrew.so. You may see broken stack traces "
  59             "in SEGV reports.");
  60     return;
  61   }
  62   acquire_my_map_info_list =
  63       (acquire_my_map_info_list_func)(uptr)dlsym(p, "acquire_my_map_info_list");
  64   release_my_map_info_list =
  65       (release_my_map_info_list_func)(uptr)dlsym(p, "release_my_map_info_list");
  66   unwind_backtrace_signal_arch = (unwind_backtrace_signal_arch_func)(uptr)dlsym(
  67       p, "unwind_backtrace_signal_arch");
  68   if (!acquire_my_map_info_list || !release_my_map_info_list ||
  69       !unwind_backtrace_signal_arch) {
  70     VReport(1,
  71             "Failed to find one of the required symbols in libcorkscrew.so. "
  72             "You may see broken stack traces in SEGV reports.");
  73     acquire_my_map_info_list = 0;
  74     unwind_backtrace_signal_arch = 0;
  75     release_my_map_info_list = 0;
  76   }
  77 }
  78 #endif
  79
  80 #if defined(__arm__) && !SANITIZER_NETBSD
  81 // NetBSD uses dwarf EH
  82 #define UNWIND_STOP _URC_END_OF_STACK
  83 #define UNWIND_CONTINUE _URC_NO_REASON
  84 #else
  85 #define UNWIND_STOP _URC_NORMAL_STOP
  86 #define UNWIND_CONTINUE _URC_NO_REASON
  87 #endif
  88
  89 uptr Unwind_GetIP(struct _Unwind_Context *ctx) {
  90 #if defined(__arm__) && !SANITIZER_MAC
  91   uptr val;
  92   _Unwind_VRS_Result res = _Unwind_VRS_Get(ctx, _UVRSC_CORE,
  93       15 /* r15 = PC */, _UVRSD_UINT32, &val);
  94   CHECK(res == _UVRSR_OK && "_Unwind_VRS_Get failed");
  95   // Clear the Thumb bit.
  96   return val & ~(uptr)1;
  97 #else
  98   return _Unwind_GetIP(ctx);
  99 #endif
 100 }
 101
 102 struct UnwindTraceArg {
 103   BufferedStackTrace *stack;
 104   u32 max_depth;
 105 };
 106
 107 _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
 108   UnwindTraceArg *arg = (UnwindTraceArg*)param;
 109   CHECK_LT(arg->stack->size, arg->max_depth);
 110   uptr pc = Unwind_GetIP(ctx);
 111   const uptr kPageSize = GetPageSizeCached();
 112   // Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
 113   // x86_64) is invalid and stop unwinding here.  If we're adding support for
 114   // a platform where this isn't true, we need to reconsider this check.
 115   if (pc < kPageSize) return UNWIND_STOP;
 116   arg->stack->trace_buffer[arg->stack->size++] = pc;
 117   if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
 118   return UNWIND_CONTINUE;
 119 }
 120
 121 void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
 122   CHECK_GE(max_depth, 2);
 123   size = 0;
 124   UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
 125   _Unwind_Backtrace(Unwind_Trace, &arg);
 126   // We need to pop a few frames so that pc is on top.
 127   uptr to_pop = LocatePcInTrace(pc);
 128   // trace_buffer[0] belongs to the current function so we always pop it,
 129   // unless there is only 1 frame in the stack trace (1 frame is always better
 130   // than 0!).
 131   // 1-frame stacks don't normally happen, but this depends on the actual
 132   // unwinder implementation (libgcc, libunwind, etc) which is outside of our
 133   // control.
 134   if (to_pop == 0 && size > 1)
 135     to_pop = 1;
 136   PopStackFrames(to_pop);
 137   trace_buffer[0] = pc;
 138 }
 139
 140 void BufferedStackTrace::SlowUnwindStackWithContext(uptr pc, void *context,
 141                                                     u32 max_depth) {
 142   CHECK_GE(max_depth, 2);
 143   if (!unwind_backtrace_signal_arch) {
 144     SlowUnwindStack(pc, max_depth);
 145     return;
 146   }
 147
 148   void *map = acquire_my_map_info_list();
 149   CHECK(map);
 150   InternalMmapVector<backtrace_frame_t> frames(kStackTraceMax);
 151   // siginfo argument appears to be unused.
 152   sptr res = unwind_backtrace_signal_arch(/* siginfo */ 0, context, map,
 153                                           frames.data(),
 154                                           /* ignore_depth */ 0, max_depth);
 155   release_my_map_info_list(map);
 156   if (res < 0) return;
 157   CHECK_LE((uptr)res, kStackTraceMax);
 158
 159   size = 0;
 160   // +2 compensate for libcorkscrew unwinder returning addresses of call
 161   // instructions instead of raw return addresses.
 162   for (sptr i = 0; i < res; ++i)
 163     trace_buffer[size++] = frames[i].absolute_pc + 2;
 164 }
 165
 166 }  // namespace __sanitizer
 167
 168 #endif  // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD ||
 169         // SANITIZER_SOLARIS